This invention relates to improvements in construction elements and more particularly relates to improvements in the structure of a joist.
In the construction of concrete buildings, joists are used to produce concrete forms for poured concrete floors and concrete pillars. The concrete-forming structures are constructed from a plurality of parallel joists spaced according to the weight distribution of the poured concrete having wooden nailers to which plywood forms are attached. These forms are held in position by a metal pipe framework and a concrete floor poured over the plywood. After the concrete hardens, the forms are stripped away by removal of the metal pipe framework. The joists and plywood are reconstructed into forms for pouring succeeding floors, unless damaged or cut to selected lengths preventing their re-use.
One type of beam used for producing concrete forms has a square cross-sectional channel into which a non-standard lumber side is inserted for use as a nailer. The use of this non-standard size has a number of disadvantages. One disadvantage is that the nails for attaching the plywood to the joist for constructing the form typically have to be hammered in at an angle creating some problems in stripping away the concrete forms as well as providing uneven surfaces in the concrete structure which must later be ground off. Another disadvantage is that they do not have sufficient strength and cannot be extended past the ends of the beam for use as a load-carrying member, forcing the compromise in their use. The bottom half of the beam has a bolt slot joined to the channel at the opposite end by a thin web. This configuration provides no method for increasing the bearing or point loads of the beam. This also does not readily permit the use of any method for attaching two or more beams together to form extensions. The thin web also offers little stability against overturning action or pressures. This type of beam is also difficult to work with to accommodate job condition size requirements. It is intended that the beams be reused and not discarded and the cutting of these beams to size defeats the purpose of their use. The prior art beams in order to produce large size concrete forms must be staggered on an intermediate stringer beam because of the lack of ability for abutting adjacent lengths.